The primary goal of the Analytical and Applied Neuroscience (AAN) Core is to be the bridge (both technically and theoretically) between clinical hypotheses and the basic neuroscience and analytical parameters required for their testing. Thus, the AAN Core provides MHCRC scientist with quantification of any analyte (endogenous or exonobiotic) that will assist in conducting an approved study or the development of a preclinical research strategy that will address the investigator's hypotheses. Moreover, this Core provides these services in conjunction with consultation about the strengths and limitations of such methods and strategies for the desired studies. The services provided are cost-efficient, and often represent assistance that the investigator either could not readily obtain, or could obtain only with extreme difficulty or expense. The core uses diverse methodologies [ranging from radioimmunoassays and High Performance Liquid Chromatography (HPLC), to HPLC-electrospray mass spectrometry (HPLC-ESMS)] to quantify such molecules that are critical to the testing of scientific hypotheses, both clinical and basic. As noted above, not only does the core implement or develop the necessary techniques and perform the assays, but it also provides consultation to clinical investigators related to study design (e.g., utility of measures, sample acquisition and storage, interpretation, etc.). Finally, with approval of the MHCRC Scientific Review Committee, this core provides analytical service and collaboration to MHCRC-associated basic scientists, and by so doing, solidifies the vital link between clinic and basic scientists and their exchange of ideas. It is the range of the services provided by the core that led to its present name. The core also provides technical assistance and resources to basic MHCRC scientists for procedures and services that their work requires, but for which they have neither sufficient expertise nor means. The key to accomplishing these ends is the ability of this core to provide state-of- the-art analytical assays of both endogenous molecules and xenobiotics (and their metabolites). During the past five years, the MHCRC has taken several steps to maximize the efficiency and responsiveness of achieving these ends. Yet it is imperative to note that the AAN Core is a single unit that provides services that were formerly the domain of three separate laboratory-based cores which had been approved in the last competing application (see below). The background and rationale for this significant change in organization are discussed in detail in Section C.1.